skip to main content

Fragile X anticipation — MRCPCH TAS MCQ

Instant feedback + full explanation. One question, done properly.

HardGeneticsFragile X anticipationMRCPCH TAS

A 7-year-old boy has learning difficulty, macro-orchidism and a long face. His mother reports premature ovarian insufficiency in her sister and tremor in her father. What is the most likely molecular mechanism?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — Expansion of a CGG repeat in FMR1

Fragile X syndrome results from CGG repeat expansion in FMR1, with premutation-associated ovarian insufficiency and tremor-ataxia in relatives. A chromosome 15q11-q13 mechanism would suggest Prader-Willi or Angelman syndrome depending on parent of origin. The pearl is that trinucleotide repeat disorders may show anticipation across generations.

Reference: Nelson Textbook of Pediatrics; RCPCH Theory examination syllabi; The Science of Paediatrics MRCPCH Mastercourse